Glues are generally liquids. In microchip package manufacture, glues are often dispensed onto a substrate using a continuous glue bead. Continuous glue beads generally comprise the same glue type and do not generally include different glue types at different places along the length of the bead.
Additional elements of a microchip package may be secured to the substrate by contacting the elements with the glue and allowing the glue to cure.
When glues are dispensed onto substrates in microchip manufacturing processes they may not flow as well as might be expected or required. Similarly, glue may flow more than desired. In some cases, flow may require to be restricted or encouraged at different places. This may be the case despite the glue being the same type and comprised within a continuous glue bead.
Different glue types have different characteristics and, in particular, exhibit different flow rates. Glue flow rate is a typical means of controlling which areas of a substrate a glue will flow onto. Glue flow rate is typically used together with a number of other factors such as the height of a glue dispensing needle above the substrate, the rate of movement of a glue dispensing needle, and the spin rate of the needle, all of which can affect the flow of a glue on a substrate. In general, therefore, present methods for controlling the flow of a glue are limited to mechanical processes.
It is common for different types of glue to be deposited in close proximity to each other. In some circumstances, problems may occur if the different glue types mix. This is particularly the case if conductive glue contaminates non-conductive glue and vice versa, as this will affect the conductive and/or non-conductive properties of each glue.
In terms of gluing, known solutions employ a multi-pass assembly approach depositing non-conductive glue, assembling and curing, and then applying conductive glue, assembling and curing. Often access to the electrical joints are restricted during the second pass requiring more complex techniques to be applied such as additional handling of the component being assembled or using a solder-ball or conductive-paste firing technique.
In camera module design, the need to support lens mounts which incorporate active components is increasing and microchip package sizes are decreasing making it more difficult to keep glues of different types separated on a substrate. Using present methods of glue flow control may result in poor reliability on electrical joints made using conductive glue where non-conductive glue has been used as part of module assembly. Often such methods result in cross contamination of glues as other elements such as lens mounts are assembled onto the substrate.